For the [url=http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=35]Superposition Principle of Wave[/url] simulatiion. You can change the wave speed and the frequency1/frequency2 for two different waves. You can also click the button labeled as "+" or "-' to change the direction for one of the wave. All the options you want are available unless you want more than two waves. We do have Fourier synthesis which combine more than two waves, but their frequency are related to each other. I do not understand why you need superposition of more than two waves? If there is no restriction, you would not find any pattern from it. It will be too complex to understand any physics out of such kind of simulation.